This may well interest the more advanced users, as this was what convinved me to go with the system I have at the moment:
http://www.ocforums.com/showthread.php?t=299042
About half way down the first page are details on the moosemod for this motherboard, allowing the Xeons to run at 800MHz FSB (Therefore at least two people have got their 2.4GHz chips to over 3.5GHz each). The main reason why the Opteron mashes the Xeons in benchmarks is because the Xeons share the same 533 bus, so pump it up to 800MHz and they fly! This type of performance is an indication of the type of speeds we can expect from the new Nocona Xeons to debut soon (Minus 64bit of course, but that will only be enabled once Win64 is released).
Unfortunately for me I paid very little for my xeons and subsequently one of the chips likes to just vanish when I perform the mod. I also had to do the following pin mod to increase the Vcore (It can't be done in BIOS
):
Well worth the money though, if you're bored of the current outlook of chips and fancy using a dual, this setups for you
2x Xeons from Ebay: £150 ($260 or so)
1x PC-DL motherboard: £130 ($225 or so)
1x 24pin PSU (470W): £60 ($105 or so)
Total price: £340 / $595
After selling my P4 system parts however, I only spent around $170, a bargain!